Homework
Assignment #7. Assigned APR 18, due TUE, APR 26 at 11:59 pm
The final is WED, MAY 4 at 10:00 am

Please look at this problem as soon as possible. Familiarity with it will
help you on the final.

Given a string consisting of a sentence, e.g.,

"my country tis of thee sweet land of libertry of thee i sing"

write a program that converts any uppercase letter in the string to a lowercase
one and determines how many times each lowercase letter occurs --this is called
the frequency. Finally it plots a histogram for all the letters. The
histogram's output would look like:

# of a's is 2XX
# of b's is 1X
# of c's is 1X
# of d's is 1X
# of e's is 8XXXXXXX
# of f's is 3XXX
# of g's is 1X
# of h's is 2XX
# of i's is 5XXXXX
# of j's is 0
# of k's is 1X
# of l's is 2XX
# of m's is 1X
# of n's is 3XXX
# of o's is 5XXXXX
# of p's is 0
# of q's is 0
# of r's is 3XXX
# of s's is 3XXX
# of t's is 6XXXXXX
# of u's is 1X
# of v's is 0
# of w's is 1X
# of x's is 0
# of y's is 3XXX
# of z's is 0

The main progam would call method histo that has the signature:
public static void histo(String s). This in turn would call method
plot that has the signature public static void plot(int[] freq).